Simple Interest

Interest is the amount that is paid on the money deposited or borrowed.Simple interest or flat rate is calculated on the original principal only. Accumulated interest from prior periods is not used in calculations for the following periods.
Thus the formula for simple interest is,
where
I - simple interest
p - principal, amount lent or borrowed
r - rate, percentage of the principal charged as interest each time period (usually a year)
n - number of periods